Bug#1087385: cmake 3.31.0-1 breaks Qt6Qml builds

[Brad King]

On Wed, Nov 13, 2024 at 11:38 AM Brad King wrote:
> > If parses fine with 3.30.5 and fails with 3.31.0.
> I can reproduce the problem locally.  I'll track it down.

The change in behavior is due to CMake 3.31 fixing this bug:

* https://gitlab.kitware.com/cmake/cmake/-/issues/25728

Here is a simple example:

```
cmake_minimum_required(VERSION 3.30)
project(DebianIssue1087385 C)
add_library(iface INTERFACE IMPORTED)
set_property(TARGET iface PROPERTY INTERFACE_INCLUDE_DIRECTORIES
"/does/not/exist")
add_executable(main main.c)
target_link_libraries(main PRIVATE iface)
```

With both 3.30.5 and 3.31.0 the simple example correctly fails:

```
CMake Error in CMakeLists.txt:
  Imported target "iface" includes non-existent path

    "/does/not/exist"

  in its INTERFACE_INCLUDE_DIRECTORIES.
```

However, if one adds the code:

```
target_include_directories(main PRIVATE
"$<TARGET_PROPERTY:iface,INTERFACE_INCLUDE_DIRECTORIES>")
```

then 3.30.5 incorrectly works due to the above-linked bug.
3.31.0 fixes that bug and now produces the correct diagnostic.

In Qt6Qml, `Qt6QmlMacros.cmake` adds that extra line in
the end of the `_qt_internal_qml_type_registration` function:

```
   target_include_directories(${effective_target} PRIVATE
         
$<TARGET_PROPERTY:${QT_CMAKE_EXPORT_NAMESPACE}::QmlPrivate,INTERFACE_INCLUDE_DIRECTORIES>
    )
```

-Brad